Prior art injection molds include a first mold plate having a portion of a mold cavity with the first mold plate disposed within a rectangular hole in a first cavity plate. The outer surfaces of the first mold plate and the inner surface of the first cavity plate are normally flush. Both the first mold plate and the first cavity plate are secured to a first supporting plate and form one-half of a complete injection mold.
The second one-half of the prior art injection mold is similar to the first one-half in that a second mold plate has the remaining portion of the mold cavity with the second mold plate disposed within a rectangular hole in a second cavity plate. Again, the outer surface of the second mold plate and the inner surface of the second cavity plate are normally flush. Both the second mold plate and the second cavity plate are secured to a second supporting plate. The second one-half of the injection mold is usually movable with respect to the first one-half and when the second mold plate is positioned adjacent the first mold plate, the complete mold cavity is formed.
Once the first and second mold plates are brought together to form the complete mold cavity, material which is to be molded is injected into the complete mold cavity and allowed to set. The second mold plate is then withdrawn and it then becomes necessary to remove the molded article from the portion of the mold cavity located within the second mold plate. This is normally done with ejector pins which are movable in unison through holes in the second support plate. The ejector pins are grouped in a pattern dictated by the contour of the portion of the mold cavity in the first mold plate.
Each time the mold plates for a different part are inserted into an injection molding machine, a new pattern for the ejector pins is normally required in order to conform to the contour of the new mold. This means that the second support plate must be replaced or the existing second support plate must be redrilled to the new pattern of ejector pins. Because of the excessive costs involved with having a separate support plate with each mold plate, the existing second support plate is normally redrilled. After numerous drillings for new patterns of ejector pins through the second support plate, the second support plate will have so many holes that there is not enough material left to accommodate new patterns of ejector pins and the support plate must be replaced.
Further, the prior art ejector pins are normally headed pins, received in sockets in an ejector carriage plate, and are secured in the sockets of the ejector carriage plate by a retaining plate, apertured to pass the shanks of the headed pins, but not their heads. Thus, to change a pattern of prior art ejector pins, an ejector housing must be disassembler from the second support plate, so that the ejector drive may be removed. Then the retainer plate must be removed so that the then existing ejector pins may be withdrawn. The carriage plate must then be redrilled to receive the new pattern of ejector pins, and, of course, accommodations must be made for the heads of the ejector pins. Eventually, of course, the prior art carriage plate, like the prior art second support plate, must be replaced because its metal will have been drilled and machined to the point that it can no longer accommodate any further patterns of ejector pins.
U.S. Pat. No. 3,930,778, the disclosure of which is hereby incorporated herein by reference, proposes a system whereby the ejector pins necessary for a particular design can be selected from a plurality of ejector pins spaced in the second support plate according to a master template. The article to be molded is positioned in such a manner with respect to the master template that a portion of the standard set of ejector pins can be utilized to eject the molded article. The ejector pins are easily reconfigured within the mold assembly without ha, ring to disassemble the mold.
The ejector pins of the U.S. Pat. No. 3,930,778 are headless pins each of which have an end portion which is received in a socket formed in the ejector carriage plate according to the master template. Each end portion is formed with an annular groove or a slot whereby a latch member may be engaged with or disengaged from the groove or slot. The ejector pin is retained within the socket when the latch member engages the groove or slot and the ejector pin is free to be removed when the latch member is withdrawn from the groove or slot.
The second support plate for the mold plate and the mold cavity are formed with a complimentary plurality of ejector pin holes to the plurality of sockets in the ejector carriage plate all according to the master template. When a new mold plate having a different mold cavity is to be assembled onto the support plate, the old mold plate must first be removed. The latch mechanism may then be slid open to release the ejector pins which may be withdrawn through the second support plate. The mold cavity of the new mold plate will have appropriate holes for ejector pins predrilled to correspond to holes in the support plate and sockets in the ejector carriage plate. The master template is used so that the positioning of the ejector holes in the mold plate will correspond with the holes in the support plate. New ejector pins are inserted in the pattern determined by the contour of the new mold cavity and the latch member is slid back to its latching position. Thus the patter of ejector pins has been changed without the necessity of drilling new holes in the support plate nor of drilling new sockets in the ejector carrying plate. A retainer plate is removably secured to the carriage plate to retain the latch members thereon. The retainer plate is also formed with a plurality of holes which correspond to the number and distribution of the holes in the support plate, and the sockets in the carriage plate all according to the master template.
The movement of the latches between their engaged and disengaged positions in the prior art U.S. Pat. No. 3,930,778 is accomplished by exerting a load on a portion of the latch that extends beyond the edges of the ejector carriage plate. There is no means in the prior art patent for locking the latches in either position and the extended portion of the latches is susceptible to either damage or interference with other components of the molding machine.
Accordingly, what is needed is a mechanism or an apparatus which simplifies the movement of the latches between their engaged and disengaged positions. The apparatus should be simple in construction, inexpensive and resolve the problems associated with the prior art latches.
The present invention provides the art with a unique apparatus for moving the latches between their engaged and disengaged positions relative to the grooves or slots in the ejector pins. The present invention utilizes a rotating cam which mates with a slot in a corresponding latch for moving the latch between its engaged and disengaged position. The rotating eccentric cam and slot within the latch are positioned with respect to one another such that the eccentric cam travels beyond center in both directions to act as a locking device to keep the latches in their engaged or disengaged position.
Other advantages and objects of the present invention will become apparent to those skilled in the art from the subsequent detailed description, appended claims and drawings.